/*
 * PrimitiveArrayTransform.java May 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.transform;

import java.lang.reflect.Array;

/**
 * The <code>PrimitiveArrayTransform</code> is used to transform
 * arrays to and from string representations, which will be inserted
 * in the generated XML document as the value place holder. The
 * value must be readable and writable in the same format. Fields
 * and methods annotated with the XML attribute annotation will use
 * this to persist and retrieve the value to and from the XML source.
 * <pre>
 *
 *    &#64;Attribute
 *    private int[] text;
 *
 * </pre>
 * As well as the XML attribute values using transforms, fields and
 * methods annotated with the XML element annotation will use this.
 * Aside from the obvious difference, the element annotation has an
 * advantage over the attribute annotation in that it can maintain
 * any references using the <code>CycleStrategy</code> object.
 *
 * @author Niall Gallagher
 */
class ArrayTransform implements Transform {

    /**
     * This transform is used to split the comma separated values.
     */
    private final StringArrayTransform split;

    /**
     * This is the transform that performs the individual transform.
     */
    private final Transform delegate;

    /**
     * This is the entry type for the primitive array to be created.
     */
    private final Class entry;

    /**
     * Constructor for the <code>PrimitiveArrayTransform</code> object.
     * This is used to create a transform that will create primitive
     * arrays and populate the values of the array with values from a
     * comma separated list of individula values for the entry type.
     *
     * @param delegate this is used to perform individual transforms
     * @param entry    this is the entry component type for the array
     */
    public ArrayTransform(Transform delegate, Class entry) {
        this.split = new StringArrayTransform();
        this.delegate = delegate;
        this.entry = entry;
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param value this is the string representation of the value
     * @return this returns an appropriate instanced to be used
     */
    public Object read(String value) throws Exception {
        String[] list   = split.read(value);
        int      length = list.length;

        return read(list, length);
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param list   this is the string representation of the value
     * @param length this is the number of string values to use
     * @return this returns an appropriate instanced to be used
     */
    private Object read(String[] list, int length) throws Exception {
        Object array = Array.newInstance(entry, length);

        for (int i = 0; i < length; i++) {
            Object item = delegate.read(list[i]);

            if (item != null) {
                Array.set(array, i, item);
            }
        }
        return array;
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param value this is the value to be converted to a string
     * @return this is the string representation of the given value
     */
    public String write(Object value) throws Exception {
        int length = Array.getLength(value);

        return write(value, length);
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param value this is the value to be converted to a string
     * @return this is the string representation of the given value
     */
    private String write(Object value, int length) throws Exception {
        String[] list = new String[length];

        for (int i = 0; i < length; i++) {
            Object entry = Array.get(value, i);

            if (entry != null) {
                list[i] = delegate.write(entry);
            }
        }
        return split.write(list);
    }
}
